1. Field of the Invention
This invention generally relates to a liquid crystal display structure. More particularly, this invention relates to a liquid crystal display structure used in a polymer stabilized alignment (PSA) liquid crystal display (LCD) to improve the image sticking effect.
2. Description of the Prior Art
Using the polymer stabilized alignment (PSA) technique in liquid crystal displays has the advantages of decreasing light leakage, improving contrast, reducing cost, and increasing transmittance. The PSA technique refers to mixing cross-linkable monomers into liquid crystals and applying voltage to liquid crystal cells to align the liquid crystals as well as the monomers mixed in the liquid crystals. Then, the monomers are cured by ultraviolet (UV) light to become cross-linked and have a particular pre-tilt angle so as to control the alignment ability of the liquid crystal and accordingly, the function of bumps can be replaced. Therefore, the dark state light leakage induced by bumps in multi-domain vertical alignment mode (MVA mode) can be reduced and the contrast can be improved.
Using UV light to cross-link the monomers mixed in the liquid crystals is time-consuming. Hence, various factors including insufficient curing time could result in uncross-linked monomers in the liquid crystals. Theses monomers may be cured by the light emitted from the backlight such as the cold cathode fluorescent lamp (CCFL) to become cross-linked and have a different pre-tilt angle resulting in the image sticking effect. Therefore, the LCD using the PSA technique is still improvable. At present, an attempt to reduce the image sticking effect is to fully cross-link the monomers mixed in the liquid crystals during the LCD manufacturing process. To achieve this goal, the percentage of the monomers mixed in the liquid crystals is decreased to as less as possible. However, this approach leads to a complicated process and substantially increases the manufacturing time.